"Clipless" types of bicycle pedals are being used by a growing number of cyclists for all types of riding. They offer improved comfort and hands free operation, over toe clips and straps, which were once more commonly used for retaining a cyclist's shoes to the pedals. Clipless pedal designs retain a cyclist's shoes to the pedals, without the use of toe clips and straps, by incorporating a form of retention mechanism, onto the pedal body, that engages a mating coupling adapter (commonly referred to as a shoe cleat), that is attached to, or made as an integral part of the sole of a cycling shoe.
With most clipless pedal systems, the cyclist attaches their shoe to the pedal, by locating their shoe cleat against the mating retention portion of the pedal, and then pressing forward, and/or down, with sufficient force to engage its resilient latching members. To release from the pedal, the cyclist rotates their foot (usually by twisting their heel away from the bicycle) a sufficient distance that causes the shoe to release from the pedal's retention mechanism. To avoid unintentional release, this rotational distance is set to be outside of the normal range of rotational movement that can naturally occur while cycling.
On all known current makes of clipless pedals, the pedal and the shoe cleat are coupled together with the use of at least one or more, resilient, spring or elastomer actuated, latching members. These are incorporated into either the pedal or the shoe cleat, depending on the particular system. Examples are described in the preferred embodiments of U.S. Pat. Nos. 4,686,867, 4,882,946, 4,942,778, 5,546,829, 5,687,619 and 5,699,699, which apply to currently available pedal systems. A serious disadvantage of all of these systems with resilient latching types of retention mechanisms, is that they are often unreliable and inconsistent to engage and disengage, and of the greatest concern, they are known to sometimes unintentionally release the cyclist's shoe from the pedal. The dangers of this cannot be overemphasized, because a cyclist could take a bad spill while having difficulty engaging or disengaging their pedals, and, in particular, the unintentional release of the cyclist's shoe from the pedal, could cause the cyclist to loose control of their bicycle, possibly with catastrophic results.
The difficulties with these resilient latching types of pedal system's retention mechanisms can occur for numerous reasons. For example, some systems are quite sensitive in design, and difficulties can arise if the shoe cleat is not properly fitted to the sole of the cycling shoe. This can be caused by a mismatch between the curvature of the sole of the shoe, and the mating shoe cleat, resulting in the shoe cleat being slightly deformed when it is attached to the shoe, adversely affecting its proper engagement with the pedal. This is particularly common with some system's which incorporate shoe cleats made from easily deformed, plastic materials. In other systems, the improper adjustment of the retention mechanism's spring tension, is often responsible for causing the system to function poorly. If the tension is set too low, for example, the shoe may inadvertently release from the pedal. Where as, if the spring tension is set too high, the cyclist may experience difficulty with, or be prevented from, engaging and/or disengaging their foot from the pedal. One of the most common causes of malfunctions with all of these pedal's retention mechanisms occurs when dirt and/or mud, etc., becomes lodged in some part of the spring/elastomer actuated components of their mechanisms, adversely affecting their proper function. The retention mechanisms described in U.S. Pat. Nos. 4,882,946, 4,942,778 and 5,687,619, for example, are so easily impaired by foreign matter that they should only be used for cycling and walking on relatively clean, hard paved surfaces. This is not always possible, of course, and can be a real inconvenience to the cyclist. In fact, there are cases of some pedal system's retention mechanisms not functioning reliably even in the best of conditions.
U.S. Pat. No. 5,553,516 describes various forms, of a shoe cleat to pedal retention mechanism, that does not rely on the use of spring/elastomer actuated latches for engagement. Also, FIG. 10 of U.S. Pat. No. 5,546,829 shows such a system. Neither of these systems are in use today, however, as it is readily apparent to those familiar with the use of clipless pedal systems, that in actual practice, these systems would be very difficult, or nearly impossible, to engage. This is because they do not provide a means for quickly and simply locating the mating portions, of the pedal and the shoe cleat, adjacent to one another for engagement. It is essential in actual use, that a cyclist of average skill is able to easily locate, and quickly engage, the pedal's retention mechanism, using natural and repeatable movements of their feet. Though it is an obvious advantage to have a simpler and more reliable retention mechanism which is not dependent on foulable, spring or elastomer actuated latches for retention, no prior art has described a system which can be simply engaged and works satisfactorily in actual practice.
A desirable feature of many clipless pedal systems, is that they can automatically release the cyclist's shoes from the pedals in the event of an accident, etc. This occurs when the feet rotate far enough to a point, where it actuates the release mechanism of the pedal, thus freeing the shoe cleats and possibly preventing injury to the joints of the cyclist, were their shoes to remain fixed to the pedals. However, some makes of clipless pedals have the disadvantage of only releasing the feet when the heels are rotated towards the outside, and this can cause injury to the cyclist if one or both of their heels are twisted towards the inside of the bicycle and the pedals do not release. Therefore, it is advantageous to have both inward and outward releasing capability for maximum safety.
Another disadvantage of many clipless bicycle pedal systems, is that they tend to be designed, rather specifically, for either road or mountain cycling use, but generally not for both. This is a disadvantage to the cyclist, because many cyclists own and use, both road and mountain bicycles, as well as road and mountain cycling shoes. The difference being, that to facilitate improved walking, mountain biking shoes have a treaded sole with a recessed area that the shoe cleat is placed within; where as road shoes, in favor of high performance, lower profile and lighter weight, sacrifice convenient walking by eliminating the treaded, rubber sole. It would be advantageous to the cyclist to have a pedal system that was equally well suited for both road and mountain cycling use, thus enabling interchangeability of their shoes and bicycles, allowing them to choose the particular combination best suited for their present need.
Yet another disadvantage common to most clipless pedal systems, is the relatively large and undesirable distance that the cyclist's foot is placed above the pedal axle. This is caused by excessive height and thickness of the pedal body, its retaining mechanism, and/or its mating shoe cleat. U.S. Pat. Nos. 4,686,867 and 5,784,931 show a couple of examples of this. Designs of this type result in a loss of efficient energy transfer from the cyclist through the pedal, as well as decreased stability of the cyclist's foot on the pedal, due to its relatively higher center of gravity over the pedal axle. Additionally, the excessive height and protruding shape of many shoe cleats, particularly with some road pedal systems, makes walking difficult and uncomfortable. It would be advantageous to have a low profile pedal for increased efficiency and stability, as well as, a low profile shoe cleat for improved walking ability.
Still another disadvantage with many pedal systems is that they use plastics, or soft metal, in the pedal bodies and/or shoe cleats of their designs. This makes them more prone to damage and can cause them to wear out, or be worn down, rather quickly while riding, or especially, when walking on the shoe cleats. Additionally, because many shoe cleats locate onto the primary load bearing, top surface of the pedal body, with the same surface that contacts the ground while walking, the wear on the shoe cleats can adversely effect the proper functioning of their connection with the pedal. In fact, when the same surface of the shoe cleat that contacts the ground while walking is used to locate the cleat on the pedal, even cleats made from hard steel will cause problems as they wear down. It would be advantageous to have a shoe cleat made from a hard steel, or other wear resistant material that locates on the pedal with a recessed surface that does not normally contact the ground while walking.
A further disadvantage of the shoe cleats used with some clipless pedals, such as those seen in U.S. Pat. No. 5,546,829, is the relatively narrow width and the small contact area of the shoe cleat against the sole of the cycling shoe. The poor support afforded by these shoe cleats can cause unwanted sideways rolling of the cyclist's shoes, which is inefficient and can lead to injury. Also, they can cause uncomfortable, localized pressure points on the balls of the cyclist's feet, beneath which they are approximately located. It is advantageous to have a shoe cleat made of a rigid material having sufficient width and contact area with the shoe sole to provide good support to the cyclist's shoes/feet.